Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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hydrochloric acid : HCl
hydrogen peroxide : H2O2
sodium acetate : CH3COONa . 3H2O
copper sulfate penta hydrate : CuSO4 . 5H2O
Class:
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elem=Cu
redox
coordination
Summary:
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Copper (II) builds a coordination complex with acetate ions. On addition
of hydrogen peroxide, this complex is destroyed and a new compound is
formed.
Description:
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Add a solution of copper sulfate to a fairly large amount of sodium acetate:
The solid dissolves in the blue liquid. The liquid becomes much darker, but
the hue of the blue does not change significantly, it just becomes much more
intense.
Add some hydrogen peroxide (appr. 10% by weight): The liquid becomes dark
brown (almost black) and becomes very viscous. The test tube can be kept
upside down, without the liquid running out of it. Inside the liquid a gas
is evolved slowly. The liquid slowly expands and changes into a viscous foam.
When the test tube is kept upside down, then the foam does not run out of
it.
Add some hydrochloric acid (appr. 10% by weight): The foam is destroyed
immediately on contact with the acid, and the gas, trapped in it, bubbles
through the liquid upwards. One can nicely see the foam being 'eaten' by
the acid. The level of clear liquid slowly goes downwards, meanwhile evolving
a lot of gas. Finally, most of the foam has dissolved, but not all of it
dissolves. When more acid is added, then the final part dissolves.
The final liquid is light blue/green.